1. Field of the Invention
The present invention relates to bumper systems for motor vehicles. More specifically, the present invention relates to an active bumper assembly to be mounted on a vehicle for lowering the impact point of a collision.
2. Description of Related Art
A motor vehicle typically has a bumper for absorbing the impact of low velocity collisions. In general, bumpers are expected to withstand the impact of a collision at a relative velocity of 5 to 15 km/h without sustaining significant damage. Many conventional bumper systems include a stationary impact absorbing structure that can deform permanently or resiliently during a collision, thereby preventing damage to the vehicle frame, adjacent components, and vehicle occupants.
The typical low-impact absorbing bumpers include a metal or plastic shell that is filled with a foamed energy-absorbing block of polypropylene or foam mounted to the vehicle on a relatively rigid beam. The foamed energy absorbing material serves to cushion the impact of a collision, by absorbing the kinetic energy through deformation of the bumper structure. However, a significant disadvantage of the conventional bumper system is that it can only withstand low velocity collisions. High velocity collisions can result in unexpected damage to the vehicle and injury to passengers.
Recently, bumper systems for motor vehicles have been designed to convert some of the kinetic energy associated with a high-speed collision into work. This is so the bumper absorbs and dissipates the energy of the impact instead of compression or deformation of the vehicle body, including the passenger compartment. If the passenger compartment is compressed or deformed, its occupants could be subject to serious injury or death. Recently developed bumper systems provide a vehicle bumper that extends longitudinally away from the passenger compartment. Such an increase in the span between the bumper and the passenger compartment increases its energy absorbing capability by increasing the fraction of the impacting vehicle""s kinetic energy that is converted into work. Although providing improvements in energy absorption, these bumper systems have not addressed the problem of vehicle compatibility.
Vehicle compatibility involves differences in vehicle characteristics between the striking vehicle and the target vehicle. Some of these characteristics include weight differences, geometry differences, differences in stiffness, and particularly differences in height off the ground. Vehicle compatibility becomes a concern when the striking vehicle and the target vehicle are mismatched, for instance, when a sport utility vehicle impacts a smaller compact car.
Conventional thinking indicates that when a larger car collides with a smaller one, the occupants of the smaller car usually fare worse. In such a collision, the smaller target vehicle undergoes a higher velocity change, and has less structure to absorb the crush. In a side impact, the larger striking vehicle is elevated with respect to the smaller target vehicle causing the brunt of the impact to be absorbed by the passenger compartment of the target vehicle, rather than striking its horizontal base member, or sill.
Since the side of the passenger compartment is often less stiff than the striking car""s front, the side of the target vehicle is strongly deformed into the passenger compartment. The smaller target vehicle potentially has less interior space to mitigate this effect of intrusion into the passenger compartment and the striking vehicle can hit the passenger of the target vehicle at speeds approximating the initial speed of the striking vehicle. The occupants of the target vehicle are severely endangered thereby.
A recent analysis of crash data reveals that larger LTV (light truck or van) to car collisions produce a significantly higher rate of fatalities than car to car collisions. For example, when LTVs strike passenger cars on the left side, the risk of death to the car driver is five times higher than the risk associated with a car to car left side impact collision. The recent increase in the percentage and number of larger vehicles, such as LTVs, currently operating has exacerbated this problem.
One concept for addressing the problem of vehicle compatibility includes activating the vehicle suspension to lower the front end of the vehicle. The front end of the vehicle is lowered by opening valves in the air shocks just before an impending collision. The disadvantage to this concept is that if false activation occurs, dropping the whole front end of the vehicle may cause loss of vehicle stability, especially if unexpected dropping occurs during certain maneuvering conditions.
Accordingly, a need exists for a bumper system that addresses the problem of vehicle compatibility. Specifically, a bumper system for the striking vehicle is needed which will better engage the sill of a target vehicle, thereby decreasing the possibility of intrusion of the striking vehicle into the passenger compartment of the target vehicle. It is also desirable to conform to space requirements and aesthetic concerns so the bumper system does not protrude too far away from the outer edge of the vehicle nose under normal operating conditions.
It is further desirable to substantially maintain the striking vehicle""s original approach angle under normal operating conditions, which is the maximum angle of an obstacle that can be approached without touching the nose of the vehicle. This is desirable so that the measure of the vehicle""s ability to commit itself to a steep rise without getting stuck or damaging the vehicle remains relatively unchanged. Furthermore, it is desirable to maintain the ramp angle, which is the included angle of a ramp that will just clear under the belly of the vehicle. If the ramp angle of the vehicle is not preserved, the vehicle will become stuck on its belly when the driver tries to cross a ridge that requires more ramp angle than the vehicle has. Therefore, it is desirable to substantially maintain the vehicle""s original approach and ramp angles underneath the vehicle so there will be enough clearance for normal and off-road vehicular conditions.
Furthermore, a need exists to maintain vehicular stability in the case of false activation of a bumper system, such that the activation of the bumper system goes virtually unnoticed by the vehicle operator.
The present invention as disclosed and claimed herewith meets these needs.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available bumper systems. Thus, the present invention provides an active bumper assembly to be mounted on a vehicle. The active bumper assembly mitigates the problems associated with vehicle compatibility by actively lowering a bumper of the striking vehicle to correspondingly lower the impact point of the target vehicle. Lowering the impact point of the target vehicle generally results in less intrusion into the passenger compartment of the target vehicle, thus preventing serious injury to the target vehicle""s occupants.
In accordance with the invention as embodied and broadly described herein in the preferred embodiment, an active bumper assembly is provided. According to one embodiment, the active bumper assembly is configured to be mounted to the front end of a motor vehicle. Alternatively, the active bumper assembly could also be mounted on the rear of a vehicle for activation in anticipation of an impending rear-end collision. The active bumper assembly may comprise an active bumper that can be connected to a motor vehicle frame by a hinge member. The active bumper could contain energy absorbing material for absorbing the impact of a striking vehicle. The active bumper assembly also includes an actuator for moving the active bumper from an inactivated position to an activated position immediately before an impending collision. A hinged locking member is also interconnected between the active bumper and the vehicle frame for securing the active bumper in the activated position. Furthermore a sensing system may be employed for sensing an impending collision and generating a signal to activate the actuator.
The active, movable bumper may be separate from the stationary bumper usually found on most motor vehicles. When the active bumper assembly is mounted to a motor vehicle, the active bumper is capable of being in an inactivated and an activated position. When the active bumper is in the inactivated position it is disposed behind the outer edge of the vehicle, namely the stationary bumper. The active bumper in this position maintains the original vehicle aesthetics as it is hidden away from view. It also maintains space requirements in this position by not extending beyond the outer edge of the vehicle under normal operating conditions. The active bumper in this position also does not extend far below the stationary bumper, thereby substantially preserving the original approach angle and ramp angle underneath the vehicle, allowing for sufficient clearance for normal and off-road vehicular conditions.
A sensing system may be included to detect an impending collision. Such sensing systems may include optical sensors utilizing lasers, microwaves or infrared sensors. Radar sensors or ultrasonic sound wave sensors could be employed. An accelerometer for measuring heavy deceleration could also be used. When a radar sensor is used, a radar antenna sends out a short, tightly focused, high-power pulse of radio waves at a known frequency. When the waves hit an object, they echo off of it and the speed of the object Doppler-shifts the echo. The antenna receives the returning signals and an impending collision would be detected.
When the sensing system detects the impending collision, it generates a signal to which the actuator responds. The actuator may be any apparatus for rapidly moving the active bumper from the inactivated position to the activated position, such as a pyrotechnic, spring, solenoid, or air pressure activator. When a pyrotechnic is used, the signal generated by the sensing system operates to flash ignite pyrotechnic material, which creates a large amount of pressure from recently formed hot gases. This pressure thrusts a piston and rod downward, applying sufficient force against the active bumper to cause it to move rapidly into the activated position.
In the activated position, the active bumper is lowered below the stationary bumper and extends beyond the stationary bumper""s outer edge. The active bumper, although moved from an inactivated to an activated position, maintains its connection to the vehicle frame by the hinge member. This movement is done without any loss of vehicle stability and goes virtually unnoticed by the operator of the striking vehicle. A hinged locking member, interconnected between the active bumper and the vehicle frame, then secures the active bumper in the activated position. The locking member prevents the active bumper from swinging back into the inactivated position upon collision with another motor vehicle by orthogonally abutting both the active bumper and the motor vehicle frame.
When the active bumper is thus configured, the impact point on the target vehicle is effectively lower than it would be if the stationary bumper had engaged the target vehicle. In the case of a sport utility vehicle colliding into a smaller compact car, the lowering of the impact point results in the sport utility vehicle engaging the horizontal base member, or sill, of the compact car, thereby reducing the amount of intrusion into the passenger compartment of the compact car, which reduces the likelihood of serious occupant injury.
The longitudinal extension of the active bumper beyond the outer edge of the stationary bumper also provides energy absorption by converting a portion of the kinetic energy of the colliding vehicles into work via the energy absorbing material contained in the active bumper. The energy absorbing material could be constructed of a variety of energy absorbing substances, such as a foamed polypropylene block, rubber, or aluminum or sheet metal arranged in a honeycomb pattern optionally filled with a wax like material. In the case of false activation, the active bumper can be reset into the inactivated position by the vehicle operator, without requiring service by the dealer or a repair shop.
These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.